EPIC Workshop 2017 SES Perspective on Electric Propulsion PRESENTED BY Eric Kruch PRESENTED ON 24 October 2017 SES Proprietary
SES Perspective on Electric Propulsion Agenda 1 Electric propulsion at SES today A. SES Fleet Overview B. Growth of Electric Propulsion in the SES fleet C. Drivers for Electric Propulsion 2 Trade Off Considerations A. Performance Trade-Offs B. System Implications considered by Operators C. Change in the Launcher Industry Landscape 3 How Electric Propulsion fits within SES Procurement 4 Conclusion A. Needed electric propulsion improvements SES Proprietary EPIC Workshop 2017 SES Perspective on Electric Propulsion 2
Electric Propulsion at SES today SES Proprietary 3
Electric Propulsion at SES today SES Fleet Overview 5 GEO satellites under procurement (4 full electric propulsion) 15 MEO satellites under procurement (8 hydrazine, 7 full electric propulsion) 4
Electric Propulsion at SES today Growth of Electric Propulsion at SES SES has been flying Electric Propulsion for over 20 years Propulsion types repartition for launched satellites SES15 (XIPS) SES12,14 (SPT140) SES17 (SPT140) 20 18 SES10 (SPT100 + Biprop) 16 SES9 (XIP + Biprop) 14 12 SES4,5 (SPT100 + Biprop) 10 8 6 4 2 0 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 Electra (PPS5000) Electric 5 Mixed Hydrazine + Arcjet Chemical
Electric Propulsion at SES today Drivers for Electric Propulsion 30 years of commercial satellites evolution from Astra 1A to SES-12 Significant evolution in payload mass and power over this period Body size: 1.5 x 1.7 x 2.1 m Dry mass: 900 Kg Launch mass: 1800 Kg Solar panel span: 19 m Payload Power: 1.6 kw 16 active transponders Body size: 2.1 x 2.35 x 5.3 m Dry mass: 4250 Kg Launch mass: 5470 Kg Solar panel span: 42 m Payload Power: 15.1 kw 76 active transponders 6
Electric Propulsion at SES today Drivers for Electric Propulsion Cost of launching a satellite has always been a barrier to entry for new satellite businesses and a huge penalty compared to terrestrial solutions In recent years, the launch industry started to address this issue through more economical but less powerful launchers, e.g. SpaceX Falcon 9, Soyuz from Kourou Due to the increasing mass of commercial satellites, some could not be launched by these launchers, despite clear economic advantage This triggered the need to reduce drastically the satellite launch mass Liquid propellants typically represent 50 to 60% of a GEO chemical propulsion satellite dry mass SES12, with a dry mass above 4200 Kg, was only made possible through an electric propulsion subsystem 7
Trade Off Considerations SES Proprietary 8
Trade-off Considerations Performance Trade-offs Launch Mass Electric propulsion offers an Operator a higher specific impulse, resulting in a lower launch mass to achieve the same on-station lifetime High thrust (typ 1-500N) and low Isp (typ 200-350 sec) for chemical propulsion Low thrust (typ < 0.3 N) and high Isp (typ>1500 sec) for electric propulsion The following table (based on a 2000Kg dry mass) illustrates the huge launch mass gain granted by electric propulsion The mass represented by an electrical solution is increasing the choice among the potential launchers which can considerably improve the launch cost 9
Trade-off Considerations Performance Trade-offs Time to Orbit BUT at the expense of the satellite time to orbit Time spent between contract signature and in-orbit delays the revenues and the satellite profitability, it is thus crucial to minimize it The following table (based on a 2000Kg dry mass) illustrates the significant duration imposed by electric propulsion 5000 4500 Falcon9 case - mass vs EOR duration Mass [Kg] 4000 3500 3000 2500 2000 100 150 200 250 300 350 400 450 EOR Duration [days] HET - Dry Mass HET - Launch Mass GIT - Dry Mass GIT - Launch Mass The higher thrust of a chemical propulsion reduces the time between launch and on-orbit, allowing the customer to have the satellite in operation quicker 10
Trade-off Considerations System implications considered by Operators (examples) (1/2) Spacecraft system design Need for increased electrical power capability, and for heavy power processing units which are highly dissipative. In combination with higher dissipative payloads, this may trigger the need for more efficient thermal control, lighter solar arrays, more efficient solar cells Plume effects, solar arrays interconnector and OSRs erosion leading to performance degradations Potential need for auxiliary propulsion system and larger reaction wheels for initial de-tumbling, safe mode, faster anomaly recoveries Space environment Low thrust => long (in the order of 200 days) orbit raising duration => increased time spent inside the Van Allen belt => extensive exposure to radiations leading to higher solar array power degradation and other potential environment effects 11
Trade-off Considerations System implications considered by Operators (examples) (2/2) Technological risk, maturity New electric thrusters with no or limited on-orbit heritage have an unknown inherent technological risk that can be evaluated only with time Most propulsion system components (valves, regulators ) are not tested with Xenon because its expensive. This could lead to potential undisclosed long term issues Schedule risk, qualification duration The timeframe for new technologies to go from concept to validation and qualification can be rather long Low thrust of electric propulsion means very long life tests 12
Trade-off Considerations Change in the Launcher Industry Landscape Future Launcher capabilities More powerful launchers coming (e.g. Falcon heavy, Ariane6) may allow to send much heavier chemical propulsion satellites to geostationary orbit On the other hand, the removal of the big constraint represented by launcher capabilities may reduce the impact related to transfer orbit duration Both chemical and electrical thrusters should thus still play a role in future satellite designs 13
How Electric Propulsion fits within SES Procurement SES Proprietary 14
How Electric Propulsion fits within SES Procurement Commercial geostationary spacecrafts are strongly dependent on financial aspects. Satellite, but also launcher, insurance and operational costs have an important weight SES is thus looking at the overall S/C in orbit price per sellable unit (where a sellable unit, e.g. classical transponder, MHz or Mbit, is depending on the target market) In the end, SES does not specify the propulsion technology, but specifies the capability, need date and price target. The satellite vendor presents the most optimal propulsion subsystem(s) to SES for each specific mission 15
Conclusion SES Proprietary 16
Conclusion Electric Propulsion Improvements For SES, electric propulsion has allowed embarking more payload and less fuel on recent satellites while staying within launcher capability. This has come at the cost of extended time to orbit, extended time to revenue, and increased time spent in higher radiative environment Potential avenues of investigation at this workshop increasing the thrust per power ratio while keeping sufficient high specific impulse combining satellites with faster electric orbit raising capability and light chemical last stage added to launchers modular S/C design approach (chemical propulsion module dedicated to orbit raising only) The launch mass benefits of electric propulsion combined with a much reduced time to orbit is highly desirable 17
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